Such an illumination device is known from WO2009099547. The known illumination device has LEDs as a light source and is a thin double-collimating light distributing device for use in a variety of general lighting applications, especially those benefiting from a slim design. Output illumination from these slim-profile illumination devices has a prescribed degree of angular collimation in each of its two orthogonal output meridians and a square or rectangular far field illumination pattern. One form of known illumination device features a single input light emitter and a single square output aperture. A second multi-segment form of the known illumination device deploys one light emitter in each engine segment, so that the total output lumens is determined by the number of segments. Both types of slim illumination devices provide input light collimated in one meridian and comprise a light distributing element that maintains input collimation while collimating output light in the un-collimated orthogonal meridian, in such a manner that the device's far-field output light is collimated in both its orthogonal output meridians. The known illumination device also includes especially structured optical films that process the engine's double-collimated output illumination so as to increase its angular extent in one or both output meridians, with maintenance of the type of beam. Although the known illumination device renders a spatially uniform light beam with sharp cutoff outside the system's adjustable far-field angular cone, it has the disadvantage that adjustment of the pre-set type of beam to a desired type of beam is rather cumbersome and has to be done by internal design, for example by addition of reflectors, and/or angular tilts.